Seasonal and interannual variability of Mediterranean Sea overturning circulation

The overturning streamfunction is a widely used metric to monitor ocean circulation changes in the North Atlantic Ocean. Analogously, it is known that an overturning circulation develops in the Mediterranean Sea, although substantially weaker and smaller than in the Atlantic. In this work we use monthly mean fields from a high-resolution ocean reanalysis (1/16◦ × 1/16◦) to explore seasonal and interannual variability of Mediterranean Sea overturning circulation in depth and water mass parameter spaces (potential density, potential temperature, salinity) from 1987 to 2018 (both included). Results show a clear single zonal clockwise transport cell in all three spaces that extends from the Strait of Gibraltar to the Levantine Basin, in which water masses tend to densify as they move eastward. This densification is mainly controlled by salinity in the Eastern Mediterranean basin (EMED), while in the Western Mediterranean (WMED) both salinity and potential temperature variations should be taken into account. In contrast, the meridional overturning transport, much more complex, is able to better capture smaller-scale variations since it responds faster to perturbations in the circulation. Seasonal variations in overturning transport are reflected in the size and strength of overturning cells in all spaces, being cells remarkably narrower in winter than in summer. Regarding interannual changes, we show that the meridional overturning transport in density space is significantly correlated with the North Atlantic Oscillation, the Mediterranean Oscillation Index and the Scandinavian pattern during wintertime in the WMED, and with the Eastern Atlantic and the East Atlantic-Western Russian in the EMED. The overturning metric in density space captures well the Eastern Mediterranean Transient, that occurred during years 1992–1996. Finally, we explore the usefulness of overturning metric to detect and track water mass changes associated to shorter scale events, using as example the strong deep convection events of years 2004–2006 in the Gulf of Lion, which marked the beginning of the Western Mediterranean Transition.J.-M. Sayol thanks the financial support by Generalitat Valenciana and the European Social Fund (ESF) through the APOSTD/2020/254 grant. Part of this research was performed during his visit to IMEDEA (UIB-CSIC), also funded by the APOSTD/2020/254 grant. D. García-García and I. Vigo are partially funded by Spanish Ministry of Science, Innovation and Universities grant number PID2021-122142OB-I00, and Generalitat Valenciana grant numbers PROMETEO/2021/030 and GVA-THINKINAZUL/2021/035

Pathways of economically relevant demersal species in the Ibiza channel from a lagrangian backtracking approach

This work studies the most probable spatial origin of demersal species that eventually reach the Ibiza Channel after a dispersion stage, a region where water masses with different characteristics choke. Demersal species are assumed to be in a planktonic stage in which they behave as passive particles, being only advected by the dominant ocean currents. To find the origin we have performed a set of backward Lagrangian simulations using a high-resolution model of currents. As a result, we obtain the preferred pathways of dispersion for demersal species. A careful analysis of pathways provides useful information on the spatiotemporal variability of demersal and their origin weeks ago before they reach the Ibiza Channel. This information is very valuable from a conservation standpoint to determine the key regions that should be protected as eggs and larvae exportation areas.Peer Reviewe

Is Greenhouse Rainwater Harvesting Enough to Satisfy the Water Demand of Indoor Crops? Application to the Bolivian Altiplano

As many other regions worldwide, the Bolivian Altiplano has to cope with water scarcity during dry periods, which in turn impacts on crop production as flood irrigation is overwhelmingly extended in the region. Since farming is the main income in the Altiplano for most families, the availability of greenhouses with water harvesting systems may represent a solution to warrant all year round production and food access. We study the daily satisfied water demand from a balance between rainfall collected by a greenhouse roof and water used for indoor crop irrigation assuming a tank is available for water storage. This balance is analyzed for 25 greenhouses spread over Batallas Municipality, close to Titicaca Lake, Bolivia, and for two case studies: (i) using irrigation data collected from farmers in the frame of a regional project; (ii) using theoretical daily water requirements assuming an intense greenhouse farming. Our evaluation includes a sensitivity analysis of relevant parameters, such as the influence of the time window of rainfall used in the simulation, the runoff coefficient, the roof surface area, the irrigation drip system, the irrigation frequency, the crop coefficient, the volume of water used for crop irrigation, and the capacity of the water tank. Overall, we find that the runoff coefficient has little impact on the satisfied demand rate, while all other parameters can play an important role depending on the greenhouse considered. Some greenhouses are able to irrigate crops normally during the wet season, while during the dry season, greenhouses are not able to satisfy more than 50% of the theoretical water requirements, even when large tanks are considered. Based on these results, we recommend the construction of greenhouses with a ground surface of <50 m2 attached to the largest available covered water tank. The information here provided can be used by stakeholders to decide their policies of investment in infrastructures in the Altiplano. Finally, the approach we follow can be applied to any other region where rainfall, temperature, and greenhouse data are available.J.-M.S thanks the financial support by Generalitat Valenciana and the European Social Fund (ESF) through the APOSTD/2020/254 grant. All authors thank funding from Generalitat Valenciana, Consellería de Participación, Transparencia, Cooperación y Calidad democrática, and from the University of Alicante, Vicerrectorado de Relaciones Internacionales y Cooperación para el Desarrollo. J.-M.S., V.A., C.E.Q., and J.-P.B.L. acknowledge support from the project “Pequeños Proyectos de Investigación” to the awarded project: “¿Son los invernaderos socioeconómica y ambientalmente sostenibles? Evaluación diagnóstico para optimizar la eficiencia de uso de agua y aprovechar el potencial productivo de los invernaderos instalados en el municipio de Batallas”, funded by Universidad Católica Boliviana San Pablo-La Paz

Mesoscale eddy variability in the Caribbean Sea

The spatial distribution, and the monthly and seasonal variability of mesoscale eddy observations derived from the AVISO eddy atlas are assessed in the Caribbean Sea during 1993–2019. The average lifetime for the whole set of eddies is 62 ± 37 days, mean amplitude of 7 ± 4 cm for cyclonic and 7 ± 4 cm for anticyclonic and mean radius of 100 ± 31 km for cyclonic and 108 ± 32 km for anticyclonic. Cyclonic eddies are on average more nonlinear than anticyclonic ones. The spatio-temporal variability in the number of eddy observations is evaluated against the Mean Eddy Kinetic Energy (MEKE) derived from geostrophic currents as well as from seasonal winds. Spatial distribution of eddy observations is correlated with MEKE while the migration of the intertropical convergence zone explains the advection of eddies towards the southern part of the basin.Open Access funding provided thanks to the CRUE-CSIC agreement with Springer Nature. JMS received the joint funding from the Generalitat Valenciana and the European Social Fund under Grant APOSTD/2020/254. AO received financial support from projects Mocca and Lamarca (grants # RTI2018-093941-B-C31 and PID2021-123352OB-C31) funded by MCIN/AEI/ and by “ERDF A way of making Europe”, and from Fundación Iberostar and Université de Toulon-VAR. MELA is funded by Corporación CE-Marin through Convocatoria 14, 2018 supporting PhD candidates

Extension and application of an observation-based local climate index aimed to anticipate the impact of El Niño–Southern Oscillation events on Colombia

The Tumaco multivariate index (TMI) is a multidecadal monthly index constructed with unique time series of sea surface temperature, surface air temperature and rain measured at Tumaco bay, in the southern Pacific coast of Colombia, and available since 1961. In this work, this index is re-evaluated after the addition of in situ sea level data, and its properties for different standardization periods are compared against oceanic El Niño–Southern Oscillation (ENSO) and other derived indices. In particular, we propose a modified TMI, hereinafter referred as TMI4, whose potential to identify the expected sign and the amount of future variations of rain induced by ENSO events in Colombia is analysed for selected extreme episodes. Results indicate that after the inclusion of sea level data, TMI4 can anticipate the development of El Niño events before the ENSO 3 and some other sea surface temperature-based regional indices, although its predictability depends on the ENSO type (canonical or Modoki). The explanation is that sea level includes new information into TMI4 on the onset of El Niño events. In particular, the signal of intraseasonal sea level anomalies carried by downwelling Kelvin waves is detected at Tumaco tide-gauge. Moreover, the analysis of the differences, both in magnitude and spatial distribution, of rainfall anomalies induced by positive (El Niño) and negative (La Niña) ENSO events characterized by TMI4 are regionally presented. As a result, we find that TMI4 is especially suited for extensive northern and western areas of mainland Colombia. For completeness, in the appendix we briefly introduce the semi-automated implementation of TMI4, including a visual interface, which is currently being tested by personnel within the operational oceanography area at Centro de Investigaciones Oceanográficas e Hidrográficas del Pacífico (Dimar-CCCP).J. M. Sayol, L. M. V asquez and J. L. Valencia thank funding from Centro de Investigaciones Oceanográficas e Hidrográficas del Pacífico – Dirección General Marítima de Colombia (Dimar), Ministry of National Defense of Colombia. J. M. Sayol also thanks the joint funding received from the Generalitat Valenciana and the European Social Fund under Grant APOSTD/2020/254. The work of DGG and IV was partially supported by Spanish Project RTI2018-093874-B-100 funded by MCIN/AEI/10.13039/501100011033 and by the Generalitat Valenciana Grant PROMETEO/2021/030. A. Orfila acknowledges financial support from FEDER/Ministerio de Ciencia, Innovación y Universidades – Agencia Estatal de Investigación through MOCCA project (grant # RTI2018-093941-B-C31)

The MEDESS-GIB database: tracking the Atlantic water inflow

García Sotillo, Marcos ... et al.-- 9 pages, 5 figures, 2 tablesOn 9 September 2014, an intensive drifter deployment was carried out in the Strait of Gibraltar. In the frame of the MEDESS-4MS Project (EU MED Program), the MEDESS-GIB experiment consisted of the deployment of 35 satellite tracked drifters, mostly of CODE-type, equipped with temperature sensor sampling at a rate of 30 min. Drifters were distributed along and on both sides of the Strait of Gibraltar. The MEDESS-GIB deployment plan was designed as to ensure quasi-synoptic spatial coverage. To this end, four boats covering an area of about 680NM2 in 6 h were coordinated. As far as these authors know, this experiment is the most important exercise in the area in terms of number of drifters released. Collected satellite-tracked data along drifter trajectories have been quality controlled and processed to build the presented MEDESS-GIB database. This paper reports the MEDESS-GIB data set that comprises drifter trajectories, derived surface currents and in situ SST measurements collected along the buoys tracks. This series of data is available through the PANGAEA (Data Publisher for Earth and Environmental Science) repository, with the following doi:10.1594/PANGAEA.853701. Likewise, the MEDESS-GIB data will be incorporated as part of the Copernicus Marine historical products. The MEDESS-GIB data set provides a complete Lagrangian view of the surface inflow of Atlantic waters through the Strait of Gibraltar and thus, very useful data for further studies on the surface circulation patterns in the Alboran Sea, and their links with one of the most energetic Mediterranean Sea flows: the Algerian CurrentThe MEDESS-GIB experiment was performed as part of the MEDESS-4MS Project activities (Project ref. 2S-MED11-01), supported by the European Regional Development Fund in the framework of the MED Programme. D. Conti is currently a PhD fellowship (FPI/1543/2013) granted by the Conselleria d’Educació, Cultura i Universitats from the Government of the Balearic Islands co-financed by the European Social Fund. J. M. Sayol is thankful for the financial support of CSIC and FSE with the JAE-pre PhD scholarship programPeer Reviewe

The MEDESS-GIB database: Tracking the Atlantic water inflow

On 9 September 2014, an intensive drifter deployment was carried out in the Strait of Gibraltar. In the frame of the MEDESS-4MS Project (EU MED Program), the MEDESS-GIB experiment consisted of the deployment of 35 satellite tracked drifters, mostly of CODE-type, equipped with temperature sensor sampling at a rate of 30min. Drifters were distributed along and on both sides of the Strait of Gibraltar. The MEDESS-GIB deployment plan was designed as to ensure quasi-synoptic spatial coverage. To this end, four boats covering an area of about 680NM2 in 6h were coordinated. As far as these authors know, this experiment is the most important exercise in the area in terms of number of drifters released. Collected satellite-tracked data along drifter trajectories have been quality controlled and processed to build the presented MEDESS-GIB database. This paper reports the MEDESS-GIB data set that comprises drifter trajectories, derived surface currents and in situ SST measurements collected along the buoys tracks. This series of data is available through the PANGAEA (Data Publisher for Earth and Environmental Science) repository, with the following doi:10.1594/PANGAEA.853701. Likewise, the MEDESS-GIB data will be incorporated as part of the Copernicus Marine historical products. The MEDESS-GIB data set provides a complete Lagrangian view of the surface inflow of Atlantic waters through the Strait of Gibraltar and thus, very useful data for further studies on the surface circulation patterns in the Alboran Sea, and their links with one of the most energetic Mediterranean Sea flows: the Algerian Current

SOCIB: the impact of new marine infrastructures in understanding and forecasting the coastal oceans: some examples from the Balearic Islands in the Mediterranean Sea

New monitoring technologies are being progressively implemented in coastal ocean observatories. As an example, gliders allow high resolution sampling, showing the existence of new features, such as submesoscale eddies with intense vertical motions that significantly affect upper ocean biogeochemical exchanges, an issue of worldwide relevance in a climate change context. SOCIB, is one of such systems, a new facility of facilities (covering from the coast to the open sea, and including among others a nearshore beach monitoring facility, HF radar, gliders and AUV’s, moorings, satellite, drifters and ARGO profilers, modelling), a scientific and technological infrastructure which is providing free, open, quality controlled and timely streams of oceanographic and coastal data and also modelling services. SOCIB takes profit of the strategic position of the Balearic Island at the Atlantic/Mediterranean transition area, one of the ‘hot spots’ of biodiversity in the world’s oceans. As an example of on-going SOCIB operations, since January 2011 sustained glider operations are in place in the Ibiza and Mallorca channels. The data centre is the core of SOCIB. The data management system created for gliders is an example of the new informatics capabilities for real time definition of mission planning, including adaptive sampling and real time monitoring using a Web tool that allows quick visualization and download. This type of new infrastructures, combined with new technologies and careful scientific analysis will allow new ways of international cooperation leading to major science breakthroughs in the very near future and new ways of science based coastal and ocean management.Peer Reviewe

On the complexity of the upper ocean mesoscale dynamics

Peer Reviewe

On the complexity of upper-ocean mesoscale dynamics

[cat] A l'oceà superficial hi tenen lloc una gran quantitat de processos físics que, tots plegats, fan que la seua dinàmica siga molt complexa. Malgrat aixì, els avanços dels últims anys en els sistemes de mesura de variables ocèaniques i en capacitat computacional permeten un estudi capa cop més acurat del mecanismes i interaccions que intervenen per crear aquesta amalgama d'estructures: remolins, filaments, fronts, ones i zones de mescla. Així, combinant l'anàlisi de dades amb models numèrics es pot inferir quins son els processos dominants que regeixen la dinàmica, la seua variabilitat espai-temporal i fer una estima del l'impacte potencial que poden tenir en la diversitat biològica o les activitats humanes relaciones amb la mar com el transport, la pesca i el turisme. En aquesta tesi doctoral s'estudien el processos físics superficials ocèanics des de diferents punts de vista i combinant diferent fonts de dades, tot centrant-se àmpliament en la Mar Mediterrània Occidental. En primer lloc, a partir dels camps de corrents d'una simulació numèrica s'estudia la circulació superficial a la Mar Mediterrània Occidental mitjançant un descriptor Lagrangià, inferint i quantificant la intrusió d'aigües atlàntiques recents al Mar Balear. Tot seguit, s'estudia el transport de massa induït pel vent superficial a les capes més superficials de la Mediterrània Occidental. Així, partint de més 16 anys de sortides diaries d'un model d'ones generades pel vent, s'estima empiricament la deriva de Stokes i s'analitza la seua interacció amb el transport d'Ekman. El transport s'integra al llarg de la columna d'aigua que és afectada pel vent. El terme d'interacció entre el transport generat directament pel vent i el generat per les ones resulta ser molt important en algunes zones, representant a certs llocs més d'un 40% de tot el transport indüit pel vent. A continuació, la disponiblitat de camps numèrics operacionals de corrents, onatge i vent s'aprofita en el disseny d'una ferramenta Lagrangiana per fer la predicció de trajectòries d'hidrocarburs i per emergències marítimes com tasques de cerca i rescat a la superfície de l'oceà. Aquesta ferramenta es basa en el llançament de partícules ideals Lagrangianes, incloent una difussivitat anisòtropa i l'arrossegament del vent. El mòdul de predicció estima la densitat de probabilitat sobre les posicions finals a curt termini (fins 3 dies), proveïnt contorns de probabilitat acumulada, molt útils per gestionar més eficientment els recursos humans i materials que participen en la resolució de crisis marítimes. Finalment, s'estudien els mecanismes de resposta de l'atmosfera davant el forçament de gradients mesoscalars de temperatura, en particular s'analitza detingudament el cas dels remolins oceànics. L'estudi es du a terme en el Pacífic Nordoest tropical combinant gairebé 20 anys d'observacions satel·litals amb simulacions numèriques. Les observacions suggereixen que el mecanisme de mescla vertical és el dominant, encara que a les simulacions numèriques si es donen les condicions adients -temperatura superficial de l'oceà, vent o mida del remolí, entre d'altres-, també té lloc el mecanisme basat en l'ajustament de l'atmosfera per gradients de pressió i per tant aquest no es pot desestimar. Els resultats de la tesi son un pas endavant en la comprensió de la complexitat dels processos ocèanics de superfície on, a més de la propia dinàmica geostròfica hi ha el vent, que genera corrents, induix mescla i favoreix la formació d'ones, interaccionant tots aquests termes entre si. A més a més s'ha mostrat que l'oceà també té un cert impacte sobre l'atmosfera, gens menyspreable en alguns casos, la qual cosa posa de relleu la necessitat d'estudiar l'oceà i l'atmosfera com sistemes acoblats entre si per tal de comprendre en profunditat la natura de la dinàmica marina.[spa] En la superficie del océano conviven una gran cantidad de procesos físicos que, todos juntos, hacen que su dinámica sea extremadamente compleja. Sin embargo, los avances recientes en los sistemas de medida de variables oceánicas y el aumento de la capacidad computacional permiten un estudio cada vez más realista de los mecanismos e interacciones que intervienen para crear esta diversidad de estructuras: remolinos, filamentos, frentes, olas y áreas de mezcla. Combinando el análisis de datos con el desarrollo de modelos numéricos se pueden inferir los procesos dominantes que rigen esta dinámica, su variabilidad espacio-temporal y hacer una estima del impacto potencial que pueden tener sobre la diversidad biológica o las actividades humanas que se desarrollan en el mar como el transporte, la pesca y el turismo. En esta tesis doctoral se estudian los procesos físicos superficiales oceánicos desde diferentes puntos de vista y combinando diversas fuentes de datos, focalizando la atención en su mayor parte en el Mar Mediterráneo Occidental. En primer lugar, a partir de los campos de corrientes de una simulación numérica se describe la circulación superficial en el Mar Mediterráneo Occidental mediante un descriptor Lagrangiano, inferiendo y cuantificando la intrusión de aguas atlánticas recientes en el Mar Balear. A continuación, se estudia el transporte inducido por el viento en las primeras capas del Mediterráneo Occidental. Así, se utilizan 16 años de salidas diarias de un modelo de oleaje para estimar la deriva de Stokes y se analiza su interacción con la corriente de Ekman. El transporte se integra a lo largo de la columna de agua influenciada por el viento. El término de interacción entre el transporte generado directamente por el viento y el generado per el oleaje resulta ser importante en algunas zonas, representando en ciertos lugares más de un 40% de todo el transporte inducido por el viento. La disponiblidad de campos numéricos operacionales de corrientes, oleaje y viento se aprovecha para el diseño de una herramienta Lagrangiana para predecir la trayectoria de derrames de hidrocarburos y para emergencias marítimas en la superficie del mar. Esta herramienta se fundamenta en el lanzamiento de partículas Lagrangianas, incluyendo una difusividad anisótropa y el arrastre del viento. El módulo de predicción estima la densidad de probabilidad sobre las posiciones finales a corto plazo (hasta 3 días), proporcionando contornos de probabilidad acumulada, muy útiles para gestionar más eficientemente los recursos humanos y materiales que participan en la resolución de crisis marítimas. Finalmente, se estudian los mecanismos de respuesta de la atmósfera ante el forzamiento de gradientes mesoescalares de temperatura, en particular se analiza el caso de los remolinos oceánicos. El estudio se lleva a cabo en el Pacífico Noroeste tropical combinando casi 20 años de observaciones satelitales con simulaciones numéricas. Las observaciones sugieren que el mecanismo de mezcla vertical es dominante, aunque en las simulaciones numéricas con las condiciones adecuadas -temperatura superficial del océano, viento o tamaño del remolino, entre otras-, también tiene lugar el mecanismo basado en el balance por gradientes de presión que por tanto no se puede desestimar. Los resultados de la tesis representan un avance en la comprensión de la complejidad del océano superficial donde, además de la propia dinámica geostrófica participa el viento, que genera corrientes, induce mezcla y favorece la formación de olas, interaccionando todos estos términos entre si. También se ha demostrado que el océano tiene cierto impacto sobre la atmósfera, no negligible en algunos casos, lo que resalta la necesidad de estudiar el océano y la atmósfera como sistemas acoplados para comprender con toda profundidad la naturaleza de la dinámica marina.[eng] At the ocean surface many physical processes coexist contributing to an extremely complex dynamics. Fortunately, recent advances in measuring systems and the increasing computational capability allow to study more realistically the mechanisms and interactions able to create the great diversity of ocean structures: eddies, filaments, fronts, waves and areas of intense mixing. Combining observations with numerical model recent developments it is possible to infer the dominant processes that govern the surface dynamics, the spatio-temporal variability and to estimate the potential impacts on the biological diversity and on human activities such as transport, fisheries and tourism. In this PhD dissertation physical processes at the ocean surface are studied from different standpoints, merging datasets and with a special focus on the Western Mediterranean Sea. First, the surface circulation in the western Mediterranean Sea is depicted departing from fields of ocean currents. These currents are obtained from a 3-year numerical simulation. By computing a Lagrangian descriptor, the Finite Size Lyapunov Exponent, it has been possible to identify and to quantify the intrusion of Atlantic waters into the Balearic Sea. Then it has been analyzed the wind induced mass transport in the upper layers of the Western Mediterranean Sea. Thus, departing from 16-year daily wave model outputs, the current generated by the Stokes drift is estimated as well as its interaction with Ekman transport terms. Mass transport is vertically integrated along the column of water that is directly affected by wind. It is shown that the interaction between Stokes and Ekman terms can be very important at some locations, where even contribute to more than 40% of the total wind induced mass transport. The availability of operational ocean models, waves and winds allow to design a Lagrangian tool to make short-term forecasts and Search ans Rescue operations at the ocean surface. This tool departs from the deployment of massless Lagrangian particles and it includes a spatiallydependent diffusivity and a wind drag term. The Lagrangian forecasting modulus estimates the kernel density of probability over the final positions of the launched particles, providing contours of accumulated probability. This is very useful to manage human and material resources involved in the resolution of crisis at sea. To conclude, it has been assessed the mechanisms by which the atmosphere responds to an ocean surface mesoscale gradient of temperature. In particular, it is studied the impact of ocean mesoscale eddies in the northwest tropical Pacific Ocean. To this aim, almost 20 years of satellite-based observations are combined with numerical simulations using an atmospheric model. Observations suggest that the response is leaded by the vertical momentum-mixing mechanism. However, numerical simulations also show the existence under certain conditions -sea surface temperature, wind or eddy propertiesof the mechanism based on pressure gradient adjustment, indicating that this mechanism should not be set aside. Results of this dissertation are a step further in our comprehension of the surface ocean complexity where, besides the geostrophic dynamics, wind has a key role generating currents, inducing mixing and waves, as well as their interactions. It has also been shown that the ocean affects the atmosphere, with a considerable influence in certain conditions. It highlights the need for studying the ocean and the atmosphere as a coupled system to acquire a deep understanding of the underlying physics